Perl中列表与数组的区别

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列表是标量的集合，数组是存储列表的变量。更精确的说，列表指的是数据，而数组指的是变量。列表的值不一定放在数组里，但每一个数组变量都一定包含一个列表（即使列表可能是空的）。

列表与数组最主要的区别在于在标量环境中：数组被解释为其长度；而列表则被解释为其最后一个元素，此时列表相当于由逗号操作符组成的表达式。

测试代码：

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@array = ( "a", "b", "c" );
$num   = @array;
$list  = ( "a", "b", "c" );
print
"The number of array elements is "$num";nThe last element of list is "$list".n";

输出结果：

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The number of array elements is "3";
The last element of list is "c".

对于子函数的返回值，同样如此。
测试代码：

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sub a {
@arr = ( "a", "b", "c" );    #返回数组的元素个数
}
 
sub b {
( "a", "b", "c" );           #返回列表的最后一个元素
}
$array = a();
$list  = b();
print
"The number of array elements is "$array";nThe last element of list is "$list".n";

输出结果：

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The number of array elements is "3";
The last element of list is "c".

  1. 明白了，但这是官方的解释吗？总觉得列表的定义怪怪的，主要是平时根本没注意到……数组被解释为长度倒是经常用

  2. 上面的解释好像是错误的！
    使用perldoc -q list可以查询到以下解释：
    What is the difference between a list and an array?
    An array has a changeable length. A list does not. An array is
    something you can push or pop, while a list is a set of values. Some
    people make the distinction that a list is a value while an array is a
    variable. Subroutines are passed and return lists, you put things into
    list context, you initialize arrays with lists, and you “foreach()”
    across a list. “@” variables are arrays, anonymous arrays are arrays,
    arrays in scalar context behave like the number of elements in them,
    subroutines access their arguments through the array @_, and
    “push”/”pop”/”shift” only work on arrays.

    As a side note, there’s no such thing as a list in scalar context.
    When you say

    $scalar = (2, 5, 7, 9);

    you’re using the comma operator in scalar context, so it uses the
    scalar comma operator. There never was a list there at all! This
    causes the last value to be returned: 9.